SEATTLE -- The violent sex offender who fled Canada earlier this month and was arrested after causing a scene in West Seattle Tuesday morning is now under investigation for possibly sexually assaulting a 16-year-old boy, according to the Seattle Police Department.

A number of residents called 911 around 6 a.m. with reports of a man yelling in an alley in the 2300 block of 44th Avenue Southwest. One of the callers told police the man threatened to attack him when he told him to be quiet.

"It was scary. But it's scarier now that I know who it was," said Rachel Brodeur, who called 911. She said she could hear the attacker make verbal threats.

"Do you have a gun? If you have a gun, come and get me. Come out here. I have a knife. I'll get you," Brodeur reported hearing.

According to police, officers arrived to find 48-year-old Michael Stanley combative and apparently intoxicated. He was arrested and booked into King County Jail for investigation of harassment, and a small knife found on him was confiscated.

But while officers were on the scene, a 16-year-old boy came over to say he was sexually assaulted by the man.

"This 16-year-old teen had no idea who Michael Stanley was," said Renee Witt with Seattle Police.

Witt said Stanley reportedly met the 16-year-old boy at a grocery store earlier Tuesday morning and went with him to an alley in the 2400 block of 44th Avenue Southwest.

"Stanley supplied the 16 year old with alcohol and at one point he apparently grabbed him from behind and sexually assaulted the teen," Witt said.

The teen reportedly pulled a knife on Stanley and ran off to contact police.

Stanley, who has a history of offenses against women and children, crossed in the United States and was found in downtown Seattle last week. He registered as a sex offender, and Canadian officials decided not to ask for extradition.

Just Monday it was revealed Stanley was living one block away from a preschool near Pike Place Market.

Ilene Stark, executive director at Pike Market Child Care and Preschool, said the community felt threatened by Stanley's arrival in the area, given that his recent history made him seem like a dangerous and unpredictable person. The preschool reviewed its lockdown plan, kept in constant contact with security in the area, and provided images and descriptions of Stanley to teachers and parents.

"It's been intense," Stark said. "It felt like there was a threat in our community and that we needed to be much more vigilant - more than in everyday life. It was disconcerting."

Stark said she was saddened that something horrible apparently had to happen before Stanley was collected by U.S. law enforcement. At the same time, she said her sadness was coupled with relief knowing that there is more legal control over Stanley's whereabouts.

Before Tuesday, there was no reason to arrest Stanley since Canada hadn't pursued an extraditable warrant and he wasn't wanted for any crimes in the United States, authorities said.

"If he continues to break the law down south you can imagine how difficult it would be for us to comment if he broke the law in different jurisdictions in the States. For us to comment on that, we couldn't keep up with that, if this was to continue," he said.

Now, some residents here hope his alleged crimes may be enough for police to keep Stanley off the streets.

"I think they should ship him right back (to Canada)," said Keith Kelly who lives nearby. "Throw away the key, right?"

Stanley is due to make his first court appearance on Wednesday.

Ed. Note: A previous version of this story said Stanley was only facing misdemeanor charges. That will no longer be the case if he is indeed charged in connection with the sexual assault of a 16 year old.